1. Field of the Invention
The invention concerns a method for severing the heads from fish with their gill cavity opened by a ventral throat cut.
2. Description of Prior Art
The beheading of fish normally occurs (see e.g. DE-PS No. 11 77 783) by a cutting penetration of the total cross-section of the fish in the region of or near the gill cavity. In order to achieve as high a yield of valuable fillet flesh as possible a device comprising two circular knives arranged at an obtuse angle to each other is preferably used, which knives penetrate the fish essentially symmetrically to its plane of symmetry.
A further known method of beheading (see e.g. DE-PS No. 15 79 416) resides in using a circular knife which is led with its cutting plane perpendicular to the plane of symmetry of the fish and cuts from the front part (Os frontale) of the cranium to the Os occipitale, the Isthmus having been severed by a throat cut. In this so-called round cut the shoulder girdle remains on the rump of the fish and can be removed before the filleting in a separate working step.
These beheading methods are not satisfactory, however, with respect to the yield of fish flesh which can be used for human consumption since it is not possible to gain the muscle flesh lying on the cranium on both sides of the web like OS occipitale superius.
Consequently it has been tried to separate the head by tearing it off after the isthmus has been separated (see NO-B 140 576). In this process the head is bent dorsally with respect to the rump and removed from the latter in this position. The result of this method is not satisfactory either since the mentioned fish pieces cannot be removed with certainty together with the muscle flesh of the fillets. The reason for this is that the shoulder girdle remaining on the fish rump is connected to the head skeleton with sinews and cords whose bases are stronger than the muscle flesh depending on the consistency of the latter. Furthermore the torn surface is disadvantageous for optical and bacteriological reasons.
3. Object of the Invention
It is therefore an essential object of the invention to propose a method for severing the heads of fish avoiding the above-mentioned deficiencies.